Exploring, drilling and completing hydrocarbon and other wells are generally complicated, time consuming, and ultimately very expensive endeavors. In recognition of these expenses, added emphasis has been placed on efficiencies associated with well completions and maintenance over the life of the well. So, for example, enhancing efficiencies in terms of logging, perforating or any number of interventional applications may be of significant benefit, particularly as well depth and complexity continues to increase.
One manner of conveying downhole tools into the well for sake of logging, perforating, or a variety of other interventional applications is to utilize slickline. A slickline is a low profile line or cable of generally limited functionality that is primarily utilized to securely drop the tool or toolstring vertically into the well. However, with an increased focus on efficiency, a slickline may be provided with a measure of power delivering or telemetric capacity. This way, a degree of real-time intelligence and power may be available for running an efficient and effective application. That is, instead of relying on a downhole battery of limited power, a manner of controllably providing power to the tool from oilfield surface equipment is available as is real-time communications between the tool and the surface equipment.
As with a less sophisticated slickline lacking power and communications, a metal wire may be utilized in a slickline equipped with power and communications. However, in the latter case, the metal wire may be configured to relay charge. Thus, in order to ensure functionality and effectiveness of the wire it may be jacketed with a polymer to insulate and prevent exposure of the wire to the environment of the well.
Of course, in order to remain effective, a jacket material may be utilized that is configured to withstand the rigors of a downhole well environment. Along these lines, a jacket material is also utilized that is intended to bond well with the underlying slickline wire. Unfortunately however, inherent challenges exist in adhering a polymer jacket material onto a metal wire. As a result, a loose point, crack or other defect at the interface of the jacket and wire may propagate as the slickline is put to use. For example, an unbonded area at the jacket and wire interface may spread as the slickline is randomly spooled from or onto a drum at the oilfield surface. If not detected ahead of time by the operator, this may lead to a failure in the jacket during use in a downhole application. Depending on the application at hand, this may translate into several hours of lost time and expense followed by a repeated attempt at performing the application.
Efforts have been undertaken to improve the bonding between the polymer jacket and underlying wire. For example, the wire may be heated by several hundred degrees ° F. before compression extruding the polymer onto the wire. In theory, a tight molded delivery of the polymer to the wire may be achieved in this way with improved bonding between the wire and the polymer.
Unfortunately, this type of heated compression extruding presents numerous drawbacks. For example, the bonding between the wire and the polymer jacket material may not always be improved. In fact, due to the different rates of cooling, with the jacket material cooling more slowly than the metal wire, the wire may shrink away from the jacket material and allow air pockets to develop at the interface between the wire and forming jacket. This not only results in a failure of adherence at the location of the air pocket but this is a defect which may propagate and/or become more prone to damage during use of the slickline. Once more, heating the wire in this manner may also reduce its strength and render it less capable in terms of physically delivering itself and heavy tools to significant well depths for a downhole application.
On a related note, extruding of the polymer jacket material as noted above is achieved by tightly and compressibly delivering the material onto the wire. That is, a markedly tight stress is imparted on the wire as the material is delivered. Again, in theory this may promote adherence between the polymer and the underlying wire. Unfortunately, while this may initially be true, compression extruding in this manner may smooth the surface of the wire as the polymer material is delivered. Thus, a long term grip on the wire by the material may be adversely affected due to the increased underlying smoothness of the wire.
Ultimately, to a large degree, efforts which have been undertaken to enhance the bond between the polymer jacket and the underlying wire have been counterproductive. Thus, challenges remain in terms of reliably utilizing a slickline with power and telemetric capacity built thereinto.